Nick Timothy is Director of the New Schools Network and a former Chief of Staff to Theresa May.

After almost seven years, more than £10 million, countless leaks, constant speculation, and the death of one of its members, we now know that the Iraq Inquiry, chaired by Sir John Chilcot, will publish its final report on 6 July.

Thanks to the leaks, we have a good idea of what to expect. A recent report in the Sunday Times predicted that Tony Blair, Jack Straw and Sir Richard Dearlove – the former head of MI6 – face “damage to their reputations” and that the Chilcot Report will be “absolutely brutal” in its verdict about the invasion of Iraq and its aftermath. In particular, the Sunday Times’ source revealed that Blair will not be “let off the hook” for allegedly offering British military support to George W Bush a full year before Iraq’s invasion. Many others – politicians, military officers, the intelligence services, and senior civil servants – will find themselves criticised severely.

But while many of those who were in positions of authority deserve their day of reckoning, the purpose of the Chilcot Report is not to point fingers. Its true purpose is, as Sir John said when he accepted the Inquiry’s chairmanship in 2009, “to establish, as accurately as possible, what happened and to identify the lessons that can be learned.” It is to make sure that, “if we face similar situations in future, the government of the day is best equipped to respond to those situations in the most effective manner in the best interests of the country.”

Of course, we already know a lot about what went wrong in Iraq. The decision to provide military support to the Americans seems to have been made by Tony Blair long in advance, in private and kept secret not just from Parliament and the public but from his own ministers and diplomats. The case for the invasion was not properly made, and the intelligence that underpinned it was spun. The planning for the aftermath of the invasion was lamentable. Specific decisions to disband the Iraqi police and army were foolish. The British Army’s performance in Basra and the south of Iraq was poor. Democracy, it turned out, requires not just elections but the rule of law, stable institutions, and a strong civil society. Far from bringing stability and prosperity to Iraq, we created a vacuum that allowed extremists and terrorists to wreak havoc.

So if – in addition to the many individual policy, governmental and operational lessons there are to be learned – there is a single, overriding lesson from Iraq, it is surely that we need to rediscover the principles of a traditional, realist, conservative foreign policy. Value stability. Respect sovereignty. Do not make foreign policy part of an ideological crusade. Do not try to recreate the world in your own image. Do not, however much you might disapprove of a dictator’s abuse of human rights, use that as a pretext for regime change. Always act on the basis of the national interest. Above all, understand the risk involved when things change in complex and volatile states.

Henry Kissinger argues that recent Western foreign policy, including Iraq, proves that “Westphalian principles” – meaning that nation states should have sovereignty over their own affairs and that this should be respected by other countries – are “the sole generally recognised basis of what exists of a world order.” Yet there is little evidence that Western governments share Kissinger’s analysis or have learned this central lesson of the Iraq War.

In 2011, as protests against President Mubarak in Cairo turned violent, Nick Clegg – who was of course Deputy Prime Minister at the time – described the so-called Arab Spring as “terribly exciting.” Some ministers saw an opportunity to side with the people, remove autocratic regimes, and bring democracy and human rights to the Middle East. Others were more cautious. In a speech about terrorism, Theresa May said: “change for the better is not inevitable…There is a chance that the Arab Spring does not bloom; that new repressive regimes replace old ones; that they give way to new and more dangerous regimes; or that terrorists gain the space and power that they lacked under the autocratic regimes of the past.”

That was a prescient warning, but it was not heeded. With Muammar Gaddafi threatening his own citizens in Benghazi, British, American and French forces not only enforced a no-fly zone to protect the city but effectively bombed the Gaddafi regime out of existence. While no Western ground troops were committed to the fighting in Libya, the result of the military intervention was – like in Iraq – the creation of a political and security vacuum. The beneficiaries have been extremists and terrorists, who see Libya as ideal territory in which they can establish themselves and plan attacks in Europe. Media reports now suggest that British special forces are already engaged in combat operations in Libya against ISIS.

Instability aids not just extremists but organised criminals too, and for this reason Libya’s descent into chaos has contributed to Europe’s migration crisis. For many years, Libya was treated by the immigration authorities as Europe’s ‘forward border’, the key transit country used by migrants to reach the continent from Africa. British immigration officials worked in the country alongside European and Libyan officials to stop illegal immigration from Africa at its source. Now the criminal gangs that smuggle people into Europe are able to work unimpeded.

Little wonder, then, that President Obama believes Libya has become a “shit show” since the removal of Gaddafi. One wonders what he would have made of Allied involvement in Syria if, in 2013, Western countries had gone ahead with the military action against Bashar Al Assad they proposed at that time. Ranged against Assad’s forces were jihadist militias including Al Nusra Front, who are associates of Al Qaeda, and the fighters who went on to form ISIS. Two years later, Western air forces launched bombing raids against the very terrorists who stood to gain from the proposed action of 2013.

This is not to say that all military action is wrong, or that the action against ISIS is wrong. ISIS pose a serious threat to British and Western security. They aim to create the world’s first truly terrorist state from which they can attack us, and they must be prevented from doing so. They will not negotiate, so they need to be destroyed. Likewise, drone strikes against terrorists in countries like Yemen are proportionate, sensible and in the interests of Western security.

But this kind of military action is very different to the interventions in Iraq and Libya. In those countries we destroyed the existing order and created an ungoverned space, and in doing so we caused huge danger not just to local people but to our own security. With the strikes against ISIS and the use of drones, we are attempting to prevent terrorists going about their work in already ungoverned spaces. In some circumstances, it might be right for Western powers to intervene to prevent atrocities, but this is not the same thing as forcing regime change or imposing a particular form of government on another country.

In Syria, the role of Western governments is not to try to build the perfect state or ideal society, it is to use the political strength and diplomatic skill we have to help reach a solution that fills the power vacuum and restores stability and security there. Doing so will undoubtedly involve coming to terms with unsavoury leaders including Assad, or at least members of his regime, and will certainly not involve democratisation or the imposition of Western standards of human rights.

This is what the Iraq War should have taught us. Of course the publication of the Chilcot Report will lead to personal recriminations and the allocation of blame – and in many cases that will be justified – but if the Inquiry is to have served its purpose, we need a grown-up debate about the nature of our foreign policy. We need to put trigger-happy liberal interventionism behind us and adopt a more traditional, cautious, realist approach. If Chilcot prompts such a change, the process will have been worthwhile – because as things stand, it is clear that we have not yet learned the lessons of Iraq.